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| CMS-PAS-HIG-24-018 | ||
| Search for Higgs boson decay to a charm quark-antiquark pair via $ \mathrm{t\overline{t}H} $ production | ||
| CMS Collaboration | ||
| 7 April 2025 | ||
| Abstract: A search for the standard model Higgs boson decaying to a charm quark-antiquark pair, $ \mathrm{H\!\to\!c\overline{c}} $, produced in association with a top quark-antiquark pair ($ \mathrm{t\overline{t}H} $) is presented. The search is performed with proton-proton collisions at $ {\sqrt{s}=13} $ TeV collected by the CMS experiment, corresponding to an integrated luminosity of 138 $ \mathrm{fb}^{-1} $. Advanced machine learning techniques are employed for jet flavor identification and event classification. The Higgs boson decay to a bottom quark-antiquark pair is measured simultaneously and the observed $ \mathrm{t\overline{t}H(H\!\to\!b\overline{b})} $ event rate relative to the standard model expectation is 0.91 $ ^{+0.26}_{-0.22} $. The observed (expected) upper limit on $ \sigma(\mathrm{t\overline{t}H})\mathcal{B}(\mathrm{H\!\to\!c\overline{c}}) $ is 0.11 ( 0.13 $ ^{+0.06}_{-0.04} $) pb at 95% confidence level (CL), corresponding to 7.8 ( 8.7 $ ^{+4.0}_{-2.6} $) times the standard model prediction. When combined with the previous search for $ \mathrm{H\!\to\!c\overline{c}} $ via associated production with a W or Z boson, the observed (expected) 95% CL interval on the Higgs-charm Yukawa coupling modifier, $ \kappa_\mathrm{c} $, is $ {|\kappa_\mathrm{c}| < 3.5} $ ($ {|\kappa_\mathrm{c}| < 2.7} $), the most stringent constraint to date. | ||
| Links: CDS record (PDF) ; Physics Briefing ; CADI line (restricted) ; | ||
| Figures | |
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Figure 1:
Distribution of b, c and light-flavor jets in the two-dimensional ParticleNet discriminant plane. The vertical and horizontal lines correspond to the edges of the tagging categories. The numbers in each bin correspond to the tagging efficiencies for b (red), c (blue) and light-flavor (yellow) jets, evaluated on a sample of simulated $ \mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{c}\overline{\mathrm{c}}) $ events. The contour lines represent constant density values for each jet flavor in steps of 5%. |
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Figure 2:
Event categorization flowchart. |
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Figure 3:
Distributions of the ParT discriminants in data (points) and predicted signal and backgrounds (colored histograms) after the maximum likelihood fit to data. The vertical bars on the points represent the statistical uncertainties in data. The hatched band represents the total uncertainty in the sum of the signal and background predictions. The lower panel shows the ratio of the data to the sum of the signal and background predictions. |
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Figure 4:
Observed and expected event yields from all SRs and CRs as a function of $ \log_{10}(S/B) $, where $ S $ are the expected $ \mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{c}\overline{\mathrm{c}}) $ (left) and $ \mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{b}\overline{\mathrm{b}}) $ (right) yields, and $ B $ are the background yields in the combined fit to data. The signals are shown for the best-fit signal strength (red), and the SM prediction, $ \mu = $ 1 (orange). The lower panel shows the ratio of the data to the post-fit background predictions, compared to the signal-plus-background predictions. |
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Figure 4-a:
Observed and expected event yields from all SRs and CRs as a function of $ \log_{10}(S/B) $, where $ S $ are the expected $ \mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{c}\overline{\mathrm{c}}) $ (left) and $ \mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{b}\overline{\mathrm{b}}) $ (right) yields, and $ B $ are the background yields in the combined fit to data. The signals are shown for the best-fit signal strength (red), and the SM prediction, $ \mu = $ 1 (orange). The lower panel shows the ratio of the data to the post-fit background predictions, compared to the signal-plus-background predictions. |
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Figure 4-b:
Observed and expected event yields from all SRs and CRs as a function of $ \log_{10}(S/B) $, where $ S $ are the expected $ \mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{c}\overline{\mathrm{c}}) $ (left) and $ \mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{b}\overline{\mathrm{b}}) $ (right) yields, and $ B $ are the background yields in the combined fit to data. The signals are shown for the best-fit signal strength (red), and the SM prediction, $ \mu = $ 1 (orange). The lower panel shows the ratio of the data to the post-fit background predictions, compared to the signal-plus-background predictions. |
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Figure 5:
Fit results of $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{b}\overline{\mathrm{b}})} $. The left panel shows the observed signal strength, compared to the expected results. The right panel shows the expected and observed significance. |
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Figure 6:
The 95% CL upper limits on $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{c}\overline{\mathrm{c}})} $. The blue and yellow bands indicate the expected 68% and 95% CL regions, respectively, under the background-only hypothesis. The vertical red line indicates the SM value $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{c}\overline{\mathrm{c}})} = $ 1. |
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Figure 7:
Constraints on the Higgs boson coupling modifiers $ \kappa_{\mathrm{c}} $ and $ \kappa_{\mathrm{b}} $. The 68% (95%) CL intervals are indicated by the dotted (solid) lines. The observed (expected) best-fit values are shown by the orange (blue) markers. |
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Figure 8:
The 95% CL upper limits on $ \mu _{\mathrm{H}{\to}\mathrm{c}\overline{\mathrm{c}}} $. The blue and yellow bands indicated the expected 68% and 95% CL regions, respectively, under the background-only hypothesis. The vertical red line indicates the SM value $ \mu _{\mathrm{H}{\to}\mathrm{c}\overline{\mathrm{c}}} = $ 1. The combination between VH and $ \mathrm{t}\overline{\mathrm{t}}\mathrm{H} $ assumes correlated theory uncertainties on the Higgs boson production cross sections and branching fractions. |
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Figure 9:
Likelihood scans of $ \kappa_{\mathrm{c}} $ with fixed $ \kappa_{\mathrm{b}}= $ 1 in the individual $ \mathrm{t}\overline{\mathrm{t}}\mathrm{H} $ (red) and VH (blue) channels and their combination (black). The 68% and 95% CL intervals are indicated by the horizontal dotted lines. |
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Figure C1:
Rejection factors of the subdominant jet flavors in each of the tagging bins. The filled bars represent the rejection factors achieved with the ParticleNet tagger and the corresponding working point definitions. The black bars represent the rejection factors achieved with the DEEPJET tagger with working points mimicking the dominant flavor tagging efficiencies. Each bin is labeled with the relative improvement of the ParticleNet tagger compared to the DEEPJET tagger. All rejection factors and tagging efficiencies are evaluated using simulated $ \mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{c}\overline{\mathrm{c}}) $ events with 2018 detector conditions. |
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Figure E1:
Confusion matrices of the ParT event classifier in the $ \text{0L} $ (upper), $ \text{1L} $ (lower left), and $ \text{2L} $ (lower right) channels after the baseline selection. For each event, the predicted label is the process with the highest output score. The event yield fractions are normalized per true label such that each row sums up to unity. |
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Figure E1-a:
Confusion matrices of the ParT event classifier in the $ \text{0L} $ (upper), $ \text{1L} $ (lower left), and $ \text{2L} $ (lower right) channels after the baseline selection. For each event, the predicted label is the process with the highest output score. The event yield fractions are normalized per true label such that each row sums up to unity. |
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Figure E1-b:
Confusion matrices of the ParT event classifier in the $ \text{0L} $ (upper), $ \text{1L} $ (lower left), and $ \text{2L} $ (lower right) channels after the baseline selection. For each event, the predicted label is the process with the highest output score. The event yield fractions are normalized per true label such that each row sums up to unity. |
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Figure E1-c:
Confusion matrices of the ParT event classifier in the $ \text{0L} $ (upper), $ \text{1L} $ (lower left), and $ \text{2L} $ (lower right) channels after the baseline selection. For each event, the predicted label is the process with the highest output score. The event yield fractions are normalized per true label such that each row sums up to unity. |
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Figure E2:
Distribution of the ParT \mathcal{D}_$ \mathrm{QCD} $ score used in the $ \text{0L} $ channel to remove the $ \mathrm{QCD} $ background. The gray area indicates the region which is rejected in the analysis. The shaded band indicates the uncertainty on the $ \mathrm{QCD} $ prediction due to limited size of simulated $ \mathrm{QCD} $ multijet samples. All contributions are normalized to unity. |
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Figure E3:
Distribution of the ParT \mathcal{D}_$ {\mathrm{t}\overline{\mathrm{t}}} {+}\text{light} $ score used to reduce the $ {\mathrm{t}\overline{\mathrm{t}}} {+}\text{light} $ background for the case of the $ \text{2L} $ channel. The gray area indicates the region which is rejected in the analysis. All contributions are normalized to unity. The last bin includes the overflow. |
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Figure E4:
Distribution of the ParT \mathcal{D}_$ {\mathrm{t}\overline{\mathrm{t}}} \mathrm{X} $ score used to define the different analysis regions for the case of the $ \text{1L} $ channel. The purple (yellow) area indicates the region which is used for the validation (analysis). The dashed line indicates the separation of signal and control regions in the analysis. All contributions are normalized to unity. |
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Figure G1:
Distributions of the ParT discriminants in data (points) and predicted signal and backgrounds (colored histograms) after the maximum likelihood fit to data in the validation region, defined by 0.4 $ < \mathcal{D}_{{\mathrm{t}\overline{\mathrm{t}}} \mathrm{X}} < $ 0.6. The vertical bars on the points represent the statistical uncertainties in data. The hatched band represents the total uncertainty in the sum of the signal and background predictions. The lower panel shows the ratio of the data to the sum of the signal and background predictions. |
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Figure H1:
Distributions of the ParT discriminants in data (points) and predicted signal and backgrounds (colored histograms) after the maximum likelihood fit to data. The vertical bars on the points represent the statistical uncertainties in data. The hatched band represents the total uncertainty in the sum of the signal and background predictions. The lower panel shows the ratio of the data to the sum of the signal and background predictions. The ratio of pre-fit expectation to the sum of the signal and background predictions after the fit is as a red line in the lower panel, including the pre-fit uncertainties as a shaded band. Uncertainties in the free-floating normalization parameters are not included in the pre-fit uncertainty band. |
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Figure H2:
On the left, observed and expected event yields from all SRs and CRs as a function of $ \log_{10}(S/B) $, where $ S $ are the observed $ {\mathrm{t}\overline{\mathrm{t}}} \mathrm{Z}(\mathrm{Z}{\to}\mathrm{c}\overline{\mathrm{c}}) $ yields, and $ B $ are the total background yields in the combined fit to data. The signals are shown for the best-fit signal strength (red), and the SM prediction, $ \mu = $ 1 (orange). The lower panel shows the ratio of the data to the post-fit background prediction, compared to the signal-plus-background predictions. On the right, fit results of $ \mu _{{\mathrm{t}\overline{\mathrm{t}}} \mathrm{Z}(\mathrm{Z}{\to}\mathrm{c}\overline{\mathrm{c}})} $ in the combination of channels (first row) and the channels individually (lower rows). The left panel shows the observed signal strength, compared to the expected results. The right panel shows the expected and observed significance. |
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Figure H2-a:
On the left, observed and expected event yields from all SRs and CRs as a function of $ \log_{10}(S/B) $, where $ S $ are the observed $ {\mathrm{t}\overline{\mathrm{t}}} \mathrm{Z}(\mathrm{Z}{\to}\mathrm{c}\overline{\mathrm{c}}) $ yields, and $ B $ are the total background yields in the combined fit to data. The signals are shown for the best-fit signal strength (red), and the SM prediction, $ \mu = $ 1 (orange). The lower panel shows the ratio of the data to the post-fit background prediction, compared to the signal-plus-background predictions. On the right, fit results of $ \mu _{{\mathrm{t}\overline{\mathrm{t}}} \mathrm{Z}(\mathrm{Z}{\to}\mathrm{c}\overline{\mathrm{c}})} $ in the combination of channels (first row) and the channels individually (lower rows). The left panel shows the observed signal strength, compared to the expected results. The right panel shows the expected and observed significance. |
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Figure H2-b:
On the left, observed and expected event yields from all SRs and CRs as a function of $ \log_{10}(S/B) $, where $ S $ are the observed $ {\mathrm{t}\overline{\mathrm{t}}} \mathrm{Z}(\mathrm{Z}{\to}\mathrm{c}\overline{\mathrm{c}}) $ yields, and $ B $ are the total background yields in the combined fit to data. The signals are shown for the best-fit signal strength (red), and the SM prediction, $ \mu = $ 1 (orange). The lower panel shows the ratio of the data to the post-fit background prediction, compared to the signal-plus-background predictions. On the right, fit results of $ \mu _{{\mathrm{t}\overline{\mathrm{t}}} \mathrm{Z}(\mathrm{Z}{\to}\mathrm{c}\overline{\mathrm{c}})} $ in the combination of channels (first row) and the channels individually (lower rows). The left panel shows the observed signal strength, compared to the expected results. The right panel shows the expected and observed significance. |
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Figure H3:
On the left, observed and expected event yields from all SRs and CRs as a function of $ \log_{10}(S/B) $, where $ S $ are the observed $ {\mathrm{t}\overline{\mathrm{t}}} \mathrm{Z}(\mathrm{Z}{\to}\mathrm{b}\overline{\mathrm{b}}) $ yields, and $ B $ are the total background yields in the combined fit to data. The signals are shown for the best-fit signal strength (red), and the SM prediction, $ \mu = $ 1 (orange). The lower panel shows the ratio of the data to the post-fit background prediction, compared to the signal-plus-background predictions. On the right, fit results of $ \mu _{{\mathrm{t}\overline{\mathrm{t}}} \mathrm{Z}(\mathrm{Z}{\to}\mathrm{b}\overline{\mathrm{b}})} $ in the combination of channels (first row) and the channels individually (lower rows). The left panel shows the observed signal strength, compared to the expected results. The right panel shows the expected and observed significance. |
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Figure H3-a:
On the left, observed and expected event yields from all SRs and CRs as a function of $ \log_{10}(S/B) $, where $ S $ are the observed $ {\mathrm{t}\overline{\mathrm{t}}} \mathrm{Z}(\mathrm{Z}{\to}\mathrm{b}\overline{\mathrm{b}}) $ yields, and $ B $ are the total background yields in the combined fit to data. The signals are shown for the best-fit signal strength (red), and the SM prediction, $ \mu = $ 1 (orange). The lower panel shows the ratio of the data to the post-fit background prediction, compared to the signal-plus-background predictions. On the right, fit results of $ \mu _{{\mathrm{t}\overline{\mathrm{t}}} \mathrm{Z}(\mathrm{Z}{\to}\mathrm{b}\overline{\mathrm{b}})} $ in the combination of channels (first row) and the channels individually (lower rows). The left panel shows the observed signal strength, compared to the expected results. The right panel shows the expected and observed significance. |
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Figure H3-b:
On the left, observed and expected event yields from all SRs and CRs as a function of $ \log_{10}(S/B) $, where $ S $ are the observed $ {\mathrm{t}\overline{\mathrm{t}}} \mathrm{Z}(\mathrm{Z}{\to}\mathrm{b}\overline{\mathrm{b}}) $ yields, and $ B $ are the total background yields in the combined fit to data. The signals are shown for the best-fit signal strength (red), and the SM prediction, $ \mu = $ 1 (orange). The lower panel shows the ratio of the data to the post-fit background prediction, compared to the signal-plus-background predictions. On the right, fit results of $ \mu _{{\mathrm{t}\overline{\mathrm{t}}} \mathrm{Z}(\mathrm{Z}{\to}\mathrm{b}\overline{\mathrm{b}})} $ in the combination of channels (first row) and the channels individually (lower rows). The left panel shows the observed signal strength, compared to the expected results. The right panel shows the expected and observed significance. |
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Figure H4:
Likelihood scans of $ \kappa_{\mathrm{c}} $ with fixed $ \kappa_{\mathrm{b}}= $ 1 (red) and floating $ \kappa_{\mathrm{b}} $ (blue). The 68% and 95% CL intervals are indicated by the horizontal dotted lines. |
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Figure H5:
Likelihood scans for the simultaneous fit of $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{b}\overline{\mathrm{b}})} $ and $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{c}\overline{\mathrm{c}})} $ (upper), $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{b}\overline{\mathrm{b}})} $ and $ \mu _{{\mathrm{t}\overline{\mathrm{t}}} \mathrm{Z}(\mathrm{Z}{\to}\mathrm{b}\overline{\mathrm{b}})} $ (lower left), and $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{c}\overline{\mathrm{c}})} $ and $ \mu _{{\mathrm{t}\overline{\mathrm{t}}} \mathrm{Z}(\mathrm{Z}{\to}\mathrm{c}\overline{\mathrm{c}})} $ (lower right). The 68% (95%) CL intervals are indicated by the dotted (solid) lines. The observed (expected) best-fit values are shown by the orange (blue) markers. |
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Figure H5-a:
Likelihood scans for the simultaneous fit of $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{b}\overline{\mathrm{b}})} $ and $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{c}\overline{\mathrm{c}})} $ (upper), $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{b}\overline{\mathrm{b}})} $ and $ \mu _{{\mathrm{t}\overline{\mathrm{t}}} \mathrm{Z}(\mathrm{Z}{\to}\mathrm{b}\overline{\mathrm{b}})} $ (lower left), and $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{c}\overline{\mathrm{c}})} $ and $ \mu _{{\mathrm{t}\overline{\mathrm{t}}} \mathrm{Z}(\mathrm{Z}{\to}\mathrm{c}\overline{\mathrm{c}})} $ (lower right). The 68% (95%) CL intervals are indicated by the dotted (solid) lines. The observed (expected) best-fit values are shown by the orange (blue) markers. |
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Figure H5-b:
Likelihood scans for the simultaneous fit of $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{b}\overline{\mathrm{b}})} $ and $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{c}\overline{\mathrm{c}})} $ (upper), $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{b}\overline{\mathrm{b}})} $ and $ \mu _{{\mathrm{t}\overline{\mathrm{t}}} \mathrm{Z}(\mathrm{Z}{\to}\mathrm{b}\overline{\mathrm{b}})} $ (lower left), and $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{c}\overline{\mathrm{c}})} $ and $ \mu _{{\mathrm{t}\overline{\mathrm{t}}} \mathrm{Z}(\mathrm{Z}{\to}\mathrm{c}\overline{\mathrm{c}})} $ (lower right). The 68% (95%) CL intervals are indicated by the dotted (solid) lines. The observed (expected) best-fit values are shown by the orange (blue) markers. |
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Figure H5-c:
Likelihood scans for the simultaneous fit of $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{b}\overline{\mathrm{b}})} $ and $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{c}\overline{\mathrm{c}})} $ (upper), $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{b}\overline{\mathrm{b}})} $ and $ \mu _{{\mathrm{t}\overline{\mathrm{t}}} \mathrm{Z}(\mathrm{Z}{\to}\mathrm{b}\overline{\mathrm{b}})} $ (lower left), and $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{c}\overline{\mathrm{c}})} $ and $ \mu _{{\mathrm{t}\overline{\mathrm{t}}} \mathrm{Z}(\mathrm{Z}{\to}\mathrm{c}\overline{\mathrm{c}})} $ (lower right). The 68% (95%) CL intervals are indicated by the dotted (solid) lines. The observed (expected) best-fit values are shown by the orange (blue) markers. |
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Figure H6:
Likelihood scans for the simultaneous fit of $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{b}\overline{\mathrm{b}})} $ and $ {\mathrm{t}\overline{\mathrm{t}}} {+}{\geq}2\mathrm{b} $ scale factor (upper left), $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{b}\overline{\mathrm{b}})} $ and $ {\mathrm{t}\overline{\mathrm{t}}} {+}\mathrm{b} $ scale factor (upper right), $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{c}\overline{\mathrm{c}})} $ and $ {\mathrm{t}\overline{\mathrm{t}}} {+}{\geq}2\mathrm{c} $ scale factor (lower left), and $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{c}\overline{\mathrm{c}})} $ and $ {\mathrm{t}\overline{\mathrm{t}}} {+}\mathrm{c} $ scale factor (lower right). The 68% (95%) CL intervals are indicated by the dotted (solid) lines. The observed (expected) best-fit values are shown by the orange (blue) markers. |
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Figure H6-a:
Likelihood scans for the simultaneous fit of $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{b}\overline{\mathrm{b}})} $ and $ {\mathrm{t}\overline{\mathrm{t}}} {+}{\geq}2\mathrm{b} $ scale factor (upper left), $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{b}\overline{\mathrm{b}})} $ and $ {\mathrm{t}\overline{\mathrm{t}}} {+}\mathrm{b} $ scale factor (upper right), $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{c}\overline{\mathrm{c}})} $ and $ {\mathrm{t}\overline{\mathrm{t}}} {+}{\geq}2\mathrm{c} $ scale factor (lower left), and $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{c}\overline{\mathrm{c}})} $ and $ {\mathrm{t}\overline{\mathrm{t}}} {+}\mathrm{c} $ scale factor (lower right). The 68% (95%) CL intervals are indicated by the dotted (solid) lines. The observed (expected) best-fit values are shown by the orange (blue) markers. |
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Figure H6-b:
Likelihood scans for the simultaneous fit of $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{b}\overline{\mathrm{b}})} $ and $ {\mathrm{t}\overline{\mathrm{t}}} {+}{\geq}2\mathrm{b} $ scale factor (upper left), $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{b}\overline{\mathrm{b}})} $ and $ {\mathrm{t}\overline{\mathrm{t}}} {+}\mathrm{b} $ scale factor (upper right), $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{c}\overline{\mathrm{c}})} $ and $ {\mathrm{t}\overline{\mathrm{t}}} {+}{\geq}2\mathrm{c} $ scale factor (lower left), and $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{c}\overline{\mathrm{c}})} $ and $ {\mathrm{t}\overline{\mathrm{t}}} {+}\mathrm{c} $ scale factor (lower right). The 68% (95%) CL intervals are indicated by the dotted (solid) lines. The observed (expected) best-fit values are shown by the orange (blue) markers. |
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Figure H6-c:
Likelihood scans for the simultaneous fit of $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{b}\overline{\mathrm{b}})} $ and $ {\mathrm{t}\overline{\mathrm{t}}} {+}{\geq}2\mathrm{b} $ scale factor (upper left), $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{b}\overline{\mathrm{b}})} $ and $ {\mathrm{t}\overline{\mathrm{t}}} {+}\mathrm{b} $ scale factor (upper right), $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{c}\overline{\mathrm{c}})} $ and $ {\mathrm{t}\overline{\mathrm{t}}} {+}{\geq}2\mathrm{c} $ scale factor (lower left), and $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{c}\overline{\mathrm{c}})} $ and $ {\mathrm{t}\overline{\mathrm{t}}} {+}\mathrm{c} $ scale factor (lower right). The 68% (95%) CL intervals are indicated by the dotted (solid) lines. The observed (expected) best-fit values are shown by the orange (blue) markers. |
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Figure H6-d:
Likelihood scans for the simultaneous fit of $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{b}\overline{\mathrm{b}})} $ and $ {\mathrm{t}\overline{\mathrm{t}}} {+}{\geq}2\mathrm{b} $ scale factor (upper left), $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{b}\overline{\mathrm{b}})} $ and $ {\mathrm{t}\overline{\mathrm{t}}} {+}\mathrm{b} $ scale factor (upper right), $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{c}\overline{\mathrm{c}})} $ and $ {\mathrm{t}\overline{\mathrm{t}}} {+}{\geq}2\mathrm{c} $ scale factor (lower left), and $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{c}\overline{\mathrm{c}})} $ and $ {\mathrm{t}\overline{\mathrm{t}}} {+}\mathrm{c} $ scale factor (lower right). The 68% (95%) CL intervals are indicated by the dotted (solid) lines. The observed (expected) best-fit values are shown by the orange (blue) markers. |
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Figure H7:
Likelihood scans for the simultaneous fit of $ {\mathrm{t}\overline{\mathrm{t}}} {+}{\geq}2\mathrm{b} $ and $ {\mathrm{t}\overline{\mathrm{t}}} {+}\mathrm{b} $ scale factors (left), and $ {\mathrm{t}\overline{\mathrm{t}}} {+}{\geq}2\mathrm{c} $ and $ {\mathrm{t}\overline{\mathrm{t}}} {+}\mathrm{c} $ scale factors (right). The 68% (95%) CL intervals are indicated by the dotted (solid) lines. The observed (expected) best-fit values are shown by the orange (blue) markers. |
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Figure H7-a:
Likelihood scans for the simultaneous fit of $ {\mathrm{t}\overline{\mathrm{t}}} {+}{\geq}2\mathrm{b} $ and $ {\mathrm{t}\overline{\mathrm{t}}} {+}\mathrm{b} $ scale factors (left), and $ {\mathrm{t}\overline{\mathrm{t}}} {+}{\geq}2\mathrm{c} $ and $ {\mathrm{t}\overline{\mathrm{t}}} {+}\mathrm{c} $ scale factors (right). The 68% (95%) CL intervals are indicated by the dotted (solid) lines. The observed (expected) best-fit values are shown by the orange (blue) markers. |
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Figure H7-b:
Likelihood scans for the simultaneous fit of $ {\mathrm{t}\overline{\mathrm{t}}} {+}{\geq}2\mathrm{b} $ and $ {\mathrm{t}\overline{\mathrm{t}}} {+}\mathrm{b} $ scale factors (left), and $ {\mathrm{t}\overline{\mathrm{t}}} {+}{\geq}2\mathrm{c} $ and $ {\mathrm{t}\overline{\mathrm{t}}} {+}\mathrm{c} $ scale factors (right). The 68% (95%) CL intervals are indicated by the dotted (solid) lines. The observed (expected) best-fit values are shown by the orange (blue) markers. |
| Tables | |
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Table 1:
Best-fit values of the $ {\mathrm{t}\overline{\mathrm{t}}} +$jets background normalization factors. |
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Table 2:
The absolute (relative) contributions to the total uncertainties, $ \Delta\mu $ ($ \Delta\mu/\Delta\mu_\text{tot} $), in the signal strength modifiers $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{c}\overline{\mathrm{c}})} $ and $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{b}\overline{\mathrm{b}})} $. The quoted values are obtained by repeating the fit while fixing the nuisance parameters associated with each category to their best-fit values, and then subtracting in quadrature the resulting uncertainty from the total uncertainty. The total uncertainty differs from the sum in quadrature of the individual components because of correlations between nuisance parameters in the fit. |
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Table A1:
Generator settings for signal and major background samples simulated with POWHEG [46-48,53,88], POWHEG -BOX-RES [50,51], or MadGraph-5_aMC@NLO [61]. The ``Groups'' column refers to the grouping of processes in the maximum likelihood fits. |
png pdf |
Table A2:
Generator settings for minor background samples simulated with POWHEG [46-48,58,60] or MadGraph-5_aMC@NLO [61]. The ``Group'' column refers to the grouping of processes in the maximum likelihood fits. |
png pdf |
Table A3:
Summary of generator settings used for modeling of the $ {\mathrm{t}\overline{\mathrm{t}}} +$jets phase space. |
png pdf |
Table D1:
Baseline selection criteria in the $ \text{0L} $, $ \text{1L} $, and $ \text{2L} $ channels. Where the selection criteria differ per year, they are quoted as 2016/2017/2018. |
png pdf |
Table E1:
Definition of the ParT event classifier discriminant for each category in the maximum likelihood fit. $ \mathcal{D}_{{\mathrm{t}\overline{\mathrm{t}}} {+}\text{jets}} $ is defined as $ \mathcal{D}_{{\mathrm{t}\overline{\mathrm{t}}} {+}\text{light}}+\mathcal{D}_{{\mathrm{t}\overline{\mathrm{t}}} {+}\mathrm{c}}+\mathcal{D}_{{\mathrm{t}\overline{\mathrm{t}}} {+}{\geq}2\mathrm{c}}+\mathcal{D}_{{\mathrm{t}\overline{\mathrm{t}}} {+}\mathrm{b}}+\mathcal{D}_{{\mathrm{t}\overline{\mathrm{t}}} {+}{\geq}2\mathrm{b}} $. |
png pdf |
Table E2:
Event yields after the fit to data in the $ \text{2L} $ channel. Values in brackets correspond to the pre-fit expectations. |
png pdf |
Table E3:
Event yields after the fit to data in the $ \text{1L} $ channel. Values in brackets correspond to the pre-fit expectations. |
png pdf |
Table E4:
Event yields after the fit to data in the $ \text{0L} $ channel. Values in brackets correspond to the pre-fit expectations. |
png pdf |
Table E5:
Event yields in the full analysis after the fit to data, separated in the SRs and CRs. Values in brackets correspond to the pre-fit expectations. |
png pdf |
Table E6:
Event yields in the full analysis after the fit to data, separated per lepton channel. Values in brackets correspond to the pre-fit expectations. |
png pdf |
Table F1:
Summary of the systematic uncertainty sources in the measurement. The first column lists the source of the uncertainty. The second (third) column indicates the treatment of correlations of the uncertainties between different data-taking periods (processes), where $ \checkmark $ means fully correlated, $ \sim $ means partially correlated (i.e., contains sub-sources that are either fully correlated or uncorrelated), and $ \times $ means uncorrelated. The last column indicates whether the uncertainties are applied to all processes or only a subset. |
png pdf |
Table H1:
Observed signal strengths as obtained by the fits using alternative background models. In brackets, the observed upper limit on the $ \mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{c}\overline{\mathrm{c}}) $ signal strengths and $ \mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{b}\overline{\mathrm{b}}) $, $ {\mathrm{t}\overline{\mathrm{t}}} \mathrm{Z}(\mathrm{Z}{\to}\mathrm{c}\overline{\mathrm{c}}) $, and $ {\mathrm{t}\overline{\mathrm{t}}} \mathrm{Z}(\mathrm{Z}{\to}\mathrm{b}\overline{\mathrm{b}}) $ significance. |
png pdf |
Table H2:
Observed normalization scale factors for the background components as obtained by the fits using alternative background models. The background normalization scale factors are given for the $ \text{2L} $ & $ \text{1L} $ ($ \text{0L} $) channels. |
| Summary |
| In summary, a search for the SM Higgs boson decaying to a pair of charm quarks via $ \mathrm{t}\overline{\mathrm{t}}\mathrm{H} $ production in the CMS experiment is presented, along with a simultaneous measurement of the background from Higgs boson decay to a bottom quark-antiquark pair. Novel jet flavor identification tools and event classification techniques using advanced machine learning algorithms are developed for this analysis. The observed $ \mathrm{t}\overline{\mathrm{t}}\mathrm{H} $ signals relative to the SM prediction are $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{c}\overline{\mathrm{c}})} = - $ 1.6 $ \pm $ 4.5 and $ \mu _{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{b}\overline{\mathrm{b}})} = $ 0.91 $^{+0.26}_{-0.22} $, respectively. The latter corresponds to an observed (expected) significance of 4.4 (4.5) standard deviations for the $ \mathrm{t}\overline{\mathrm{t}}\mathrm{H}(\mathrm{H}{\to}\mathrm{b}\overline{\mathrm{b}}) $ process. The observed (expected) upper limit on $ \sigma_{\mathrm{t}\overline{\mathrm{t}}\mathrm{H}}\mathcal{B}_{\mathrm{H}{\to}\mathrm{c}\overline{\mathrm{c}}} $ is 0.11 (0.13 $^{+0.06}_{-0.04} $)\unitpb, corresponding to 7.8 (8.7 $ ^{+4.0}_{-2.6} $) times the theoretical prediction for an SM Higgs boson mass of 125.38 GeV. When combined with the previous search for $ \mathrm{H}{\to}\mathrm{c}\overline{\mathrm{c}} $ via associated production with a W or Z boson, the observed (expected) 95% CL interval on the Higgs-charm Yukawa coupling modifier, $ \kappa_{\mathrm{c}} $, is $ {|\kappa_{\mathrm{c}}| < 3.5} $ ($ {|\kappa_{\mathrm{c}}| < 2.7} $). This represents the most stringent constraint on $ \kappa_{\mathrm{c}} $ to date. |
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